A red meat allergy caused by ticks is rising in the U.S. Canada's national health agency says it's rare here
Experts say the issue is on their radar, though it's unclear how many cases have been found here
A tick that's creating some concern in the U.S. for causing a rise in red meat allergies has already been found in Canada, but experts say cases here are rare for now.
The culprit behind this allergy, the lone star tick, has been moving further north for years now due to favourable conditions linked to climate change. That's a worrisome trend for some researchers, as little is known about how to treat the condition that comes from the tick's bite.
This week new concerns were raised by health experts in the United States after a report published Thursday by the Centers for Disease Control and Prevention (CDC) found an increasing number of people have become allergic to red meat in recent years.
Since 2010, more than 100,000 people in the U.S. have developed alpha-gal syndrome (AGS) — the condition that causes the red meat allergy — from a lone star tick bite.
A second report estimated that it could actually be 450,000 people who have AGS — making it the 10th most common allergy in the U.S., according to Scott Commins, a University of North Carolina researcher who co-authored both reports.
Health officials believe that many people likely don't even know they have the condition.
In an email to CBC News, the Public Health Agency of Canada (PHAC) said the lone star tick transmits other types of disease-causing bacteria to humans and that developing an allergy to red meats from it is rare.
Even though the tick has been found in parts of the country, PHAC said to its knowledge, the tick isn't "established" here and there's no "evidence of populations" of the lone star tick.
It said the ticks being found are likely "adventitious" ones that are being carried into Canada by migratory birds.
"The risk of exposure to adventitious ticks is very low and, as a result, development of an allergy from these bites would also be very low," reads part of the statement.
But PHAC said it anticipates the tick will eventually become established in the country, so it has developed an approach to predict where it's likely to reside.
CBC News breaks down what we know about the tick and the allergies it causes.
What is alpha-gal syndrome (AGS)?
AGS is an allergic condition to red meat that develops after a lone star tick bite. The tick got its name from the white dot or lone star on the back of the female.
When the tick bites a person, it spits alpha gal — a sugar — into the blood.
This sugar is found in meat from mammals, like beef, pork and lamb, and also in tick spit.
Humans normally harmlessly digest it when eating meat, but when it appears elsewhere in a person's body like the bloodstream, it causes a strong reaction.
The body creates antibodies to fight it and this battle causes symptoms that can range from a general rash to a severe anaphylactic reaction.
Once infected, if the person eats meat from mammals or ingests gelatin or other mammal products, they can experience symptoms.
The study released Thursday by the CDC examined test results from 2017 and 2022 from the main U.S. commercial lab looking for alpha-gal antibodies. It found that the number of people testing positive increased from about 13,000 in 2017 to 19,000 in 2022.
Experts say cases may be up for a variety of reasons, including lone star ticks' expanding range, more people coming into contact with the ticks or more doctors learning about it and ordering tests.
Dr. Mariam Hanna, who is an allergist and pediatrics chair of the Canadian Society of Allergy and Clinical Immunology, said the allergist community is aware of AGS as it's been around for the last decade.
"It's definitely on our radar," Hanna said, adding that she's more concerned with other tick-borne illnesses, like Lyme disease.
What are the symptoms?
Some people bitten by lone star ticks will develop a circular rash, which is similar to that of early Lyme disease.
People with the condition can experience hives, nausea, vomiting, diarrhea, severe stomach pain, difficult breathing, dizziness and swelling of the lips, throat, tongue or eye lids.
Unlike some other food allergies, where symptoms usually take place right after eating, this reaction can hit hours later.
This delayed reaction, said Hanna, causes the syndrome to be a bit "mysterious" and makes it difficult to diagnose.
There is currently no treatment. U.S. health officials are not aware of any confirmed deaths from the allergy.
"With those diagnosed with this syndrome their best bet is avoidance [of mammalian meats]," said Hanna.
She added that if people accidentally consume something that can trigger a reaction, they should treat it like an anaphylaxis and use an epi-pen.
After any tick bite, Health Canada advises people to consult a healthcare provider if they develop symptoms and take note of where on their body they were bitten, how long the tick might have been attached and where they were when bitten by the tick.
Where is the lone star tick found?
The lone star tick is usually found in the eastern, southeastern and south-central parts of the United States, but over the last several years, it has moved north.
Justin Wood, founder of private tick testing company Geneticks Canada, said it's difficult to track alpha-gal because it's not a pathogen in the tick.
So instead, his company tracks the lone star ticks themselves.
"This year in particular has been quite bad, we normally don't see really any submitted to us, maybe one or two throughout the year," he said.
And eTick, a website that tracks ticks in Canada, said 21 were identified in Ontario so far this year.
Wood said the ticks' increasing presence in Canada is concerning.
"The fact that our climate is becoming hospitable to these types of ticks has really kind of dramatic effects for what we might see in other species of ticks [and] what kinds of pathogens we might see moving in," he said. "It's almost kind of an indicator species."
Can the allergy go away?
According to Commins, the allergy can go away in some people. He said he's seen that happen in about 15 per cent to 20 per cent of his patients. But a key is avoiding being re-bitten.
"The tick bites are central to this. They perpetuate the allergy," he said.
Corrections
- An earlier version of this story said CBC News received comment from Health Canada. In fact, it received comment from the Public Health Agency of Canada.Jul 31, 2023 9:55 AM ET
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With files from Lauren Pelley, The Associated Press